Nasal delivery of a substance (e.g., a drug, a vaccine, etc.) can be useful both for treating diseases or disorders of the nasal passageways themselves and for treating other disorders or conditions through the systemic route (e.g., vaccine, neurological, etc.). The advantages of nasal delivery of a substance are, among others, the following:
(a) a rich vascular plexus—a direct route into the blood stream; (b) avoiding gastrointestinal destruction as drug degradation which is observed in the gastrointestinal tract is absent. (c) Hepatic first pass metabolism (destruction of drugs by liver enzymes) is absent; (d) rates of absorption and plasma concentrations are comparable to intravenous administration; (e) ease, convenience and safety; (f) rapidly achievement of therapeutic brain and spinal cord (CNS) drug concentrations; (g) rapid drug absorption and quick onset of action can be achieved; (h) the bioavailability of larger drug molecules can be improved by means of absorption enhancers or other approaches; (i) The nasal bioavailability for smaller drug molecules is good; (j) drugs that are orally not absorbed can be delivered to the systemic circulation by nasal drug delivery; (k) based on published information, the nasal route was indicated as an alternate to parenteral route, especially for protein and peptide drugs; (l) convenient for the patients, especially for those on long term therapy, when compared with parenteral medication.
On the other hand, the limitations of nasal delivery of a substance are:
(a) the histological toxicity of absorption enhancers used in nasal drug delivery system is not yet clearly established; (b) relatively inconvenient to patients when compared to oral delivery systems since there is a possibility of nasal irritation; (c) nasal cavity provides smaller absorption surface area when compared to (Gastro intestinal tract GIT).
Therapy through intranasal administration has been an accepted form of treatment in many countries. In recent years many drugs have been shown to achieve better systemic bioavailability through nasal route than by oral administration. Advances in biotechnology have made available a large number of protein and peptide drugs for the treatment of a variety of diseases. These drugs are unsuitable for oral administration because they are significantly degraded in the gastrointestinal tract or considerably metabolized by first pass effect in the liver. Also, the parenteral route is inconvenient for long term therapy. Of many alternate routes tried, intranasal drug delivery is found much promising for administration of such drugs.
There are many traditional devices that are adapted to supply substances to the nasal cavity. These devices include, for example, syringed nose drops, pump spray devices, and fluorinated propellant metered dose inhalers (MDI). These traditional devices have not generally been able to achieve the particle sizes necessary to maximize efficacy while helping mitigate undesired pulmonary absorption. For example, both eye dropper type devices and simple spray devices typically present medicament into the nasal cavity in a stream. The result is that much of the medicament simply runs out of the patient's nose, and only a small amount of the drug is absorbed, with even less of the drug reaching the nasal epithelia.
In the recent years a few companies have developed novel drug delivery devices which are activated when a subject exhales air from the lungs through the mouth. As a result of the air exhale, the soft palate is closed, and thereby operates to isolate the nasal passageways from the remainder of the pulmonary system. By that, the soft palate acts as a natural check valve preventing the flow of air between the lungs and the nasal cavity. Thus, in these air-exhale based devices, it is believed that nasal substance delivery can be improved if the patient is exhaling orally while the substance is being sprayed into the nasal passages. One nasal delivery device that takes advantage of this phenomenon is shown in U.S. Pat. No. 6,715,485 to Optinose. This patent application discloses a delivery device for delivering a substance to the nasal airway of a subject, in particular the posterior region of the nasal airway, the delivery device comprising: a closure unit for causing the closure of the oropharyngeal velum of the subject, and a delivery unit for delivering a gas flow entraining a substance to one of the nostrils of the subject at such a driving pressure as to flow around the posterior margin of the nasal septum and out of the other nostril of the subject, wherein the delivery unit comprises a nosepiece which includes an outlet through which the gas flow in use is delivered to the one nostril and a sealing member for sealing the one nostril to the outlet such as in use to prevent the escape of the gas flow through the one nostril.
The present invention takes advantage of the normal swallowing mechanism in which the soft palate closes, in the delivery process of a substance to nose. In this mechanism the isolation of the nose passageways from the respiratory system is better than in the case of air exhalation (on which the nasal drug delivery devices known in the prior art is based). Furthermore, the present invention is able to deliver a desired amount of substance to the nasal epithelium while preventing entry into the pulmonary tract and the lungs. This substance delivery device has to comply with the following key requirements: a. they have to be accurate in the doses of the substance they provide, b. good penetration to the nasal canals, c. painless, d. with minimal stomach deposition, e. with minimal lung deposition, f. easy to use, g. with improved patient compliance, h. washing of the drug flavor, i. suitable platform for various drugs and vaccines, j. and with subject-independent actuation. The present invention is intended to comply with all these requirements.